In this paper, we have investigated the generation of pretilt angle for nematic liquid crystal (NLC) in a cell with oblique non-polarized ultraviolet(UV) light irradiation polyimide (PI) surface. It was found that the monodomain alignment of the NLC is obtained with an angle of incidence of 70∼85。 on PI surface. It is considered that the monodomain alignment of NLC is attributed to anisotropic of NLC is about 3。 with and angle of incidence of 70∼75。. Finally, we observed that the voltage-transmittance, response time, and voltage-holding-ratio(VHR) characteristics of photo-aligned twisted nematic(TN)-LCD with and angle of incidence of 85。 on PI surface were almost same compared to rubbing -treated TN-LCD.